1. Field of the Invention
This invention relates to disazo dyestuffs and the method for forming such materials.
2. Description of Prior Art
Various dyestuffs containing the monohalogenotriazine group have been known. Because of the presence of this reactive triazine group, they react easily with cellulose fibers, such reaction normally being carried out in the presence of an acid binding agent such as sodium carbonate. For example, in cases where the liquor-to-goods ratio is relatively great, these dyestuffs give fast and practical dyeing using the dip dyeing method in which fibers are treated in the dye bath at an elevated temperature, 60.degree. to 90.degree. C, in the presence of a salt and an acid binding agent. When these dyestuffs are employed for dyeing methods using smaller liquor-to-goods ratios, as, for instance, the pad dyeing method or the printing method, they can be satisfactorily fixed on cellulose fibers by short periods of steam heating or dry heating in the presence of an acid binding agent. In the case of these known dyestuffs having the monohalogenotriazine group, it is practically impossible to completely fix all of the absorbed dyestuff onto the cellulose fibers, and a considerable amount of non-fixed dyestuff is always present in the cellulose fibers immediately after dyeing. Accordingly, these dyed cellulose fibers exhibit very poor wet fastness, especially when measured by the fastness to washing test (JIS L-0844) or fastness to water test (JIS L-0846). (JIS = Japanese Industrial Standard.) It is necessary then, in order to attain a high wet fastness, to remove the non-fixed dyestuffs. Such removal is commonly carried out by treating the fabric with a suitable surface active agent in a hot soaping step. However, in practice, such treatment requires a long time, occupying many complicated steps in comparison to the relatively simple dyeing procedure. Therefore, it has been acknowledged that dyestuffs having the monohalogenotriazine group are commerically unsatisfactory in that the overall dyeing procedure cannot be performed efficiently. Thus, the development of triazine dyestuffs of this type which show excellent wet fastness without performing the above-mentioned hot soaping steps has been greatly demanded in the art.